New immunosuppressive techniques continue to increase the long- term graft survival of clinical renal transplants. There has been little progress, however, in improving the quality or duration of renal preservation. The proposed research is a comprehensive study of the mechanism of renal injury in preserved kidneys. In particular, we will examine the roles of: a) Ca, b) O2 free radicals, and c) microcirculatory changes in the loss of renal function after transplantation. We will use 3- and 5-day preserved dog kidney models to study the mechanism of kidney injury. In earlier studies we were unable to detect major metabolic differences between 3-day (viable) and 5- day (marginally viable) preserved kidneys at the end of preservation; this suggests that functional differences become apparent only after reperfusion. The extent, type, and rate of onset of renal injury will be analyzed for periods of 15 minutes to 24 hours during kidney reperfusion, using perfusor dog or transplantation models. We will use several techniques to assess the extent and type of injury: a) biochemical techiques (mitochondria, microsomes, lipid metabolism, Ca metabolism, lipid peroxide formation, calmodulin, adenine nucleotides, cyclic AMP, and membrane permeability studies); b) physiological techniques (total renal blood flow, renal cortical microcirculation, glomerular filtration rate, percent Na reabsorption, urine/plasma protein ratio, and urine production); and c) morphological techniques (electron microscopy and microangiogram). Identifying the mechanism of kidney injury will allow the appropriate selection of specific drugs to test in the dog model. Drugs likely to be appropriate include Ca antagonists (plasma membrane-active, intracellular-active, or both), phospholipase inhibitors, calmodulin inhibitors, O2 free radical scavengers, and vasoactive agents. We will evaluate how these drugs affect the mechanism of renal damage and how they relate to improve renal function. Renal function and long-term survival in the transplantation model will be the final test of perfusate modification and drug therapy. The long-range of this research is the consistent, successful preservation of kidneys for at least 5 days.